1. Field of the Invention
The present invention generally relates to test boards and test methods using the same, and more particularly, to a test board and a test method using the same suitable for testing a semiconductor chip, a circuit board, or a semiconductor device having projection electrodes.
2. Description of the Related Art
Recently, demands for high-density, high-speed semiconductor devices and further reduction in a size thereof are growing. To meet such demands, a plurality of bare semiconductor chips not sealed in a package or a plurality of semiconductor devices having a ball grid array (BGA) structure may be directly mounted on a circuit board.
According to such a mounting method, the entire device becomes an inferior product if one of the plurality of bare chips or semiconductor devices has a defect. Therefore, a high level of reliability is required in individual bare chips or semiconductor devices.
Hence, a growing importance is attached to a test for determining whether each of the individual bare chips or semiconductor devices is operating properly.
Various methods for testing devices having projection electrodes on the lower surface thereof are proposed and practiced. These devices include a bare chip not sealed in a resin package, a semiconductor device sealed in a resin package, a circuit board on which semiconductor devices are mounted.
When a device having projection electrodes is tested for electrical connection, the tested device should be connected to bumps. Care must be taken so that the bumps may not be deformed or transformed when they are connected to the electrodes.
FIG. 1 shows how a semiconductor device 51 is mounted on a test board 50 according to a related art. As shown in FIG. 1, the test board 50 comprises an insulating plate 53, a conductive part 54 and a land part 55. The insulating plate 53 is embodied, for example, by an insulating tape. A hole 56 is formed in the insulating plate 53 so as to face a projection electrode 52 (bump) provided in the semiconductor device 51.
The conductive part 54 is provided on that surface of the insulating plate 53 opposite to the surface on which the semiconductor device 51 is mounted. The conductive part 54 is connected to a testing apparatus (not shown) so that a test is conducted on the semiconductor device 51 by connecting the conductive part 54 to the associated projection electrode 52.
The land part 55 is provided in the hole 56 formed in the insulating plate 53. The end of the land part 55 projects from the insulating plate 53. The land part 55 is electrically connected to the conductive part 54 so that, by mounting the semiconductor device 51 on the test board 50, the projection electrode 52 comes into contact with the land part 55 and is electrically connected to the conductive part 54.
Therefore, it is possible to test the semiconductor device 51 using the testing apparatus connected to the test board 50. Usually, a pressing mechanism (not shown) presses the semiconductor device 51 against the test board so as to ensure that the projection electrode 52 is electrically connected to the land part 55 properly. Due to the pressing mechanism, an increased amount of connection pressure is provided between the projection electrode 52 and the land part 55 so that the proper electrical connection is established.
With the recent trend for high-density, compact semiconductor devices, the projection electrodes 52 are provided at an increasingly finer pitch. Associated with this, the size of the projection electrode 52 is becoming smaller. As the pitch of the projection electrode 52 becomes finer and the size thereof becomes smaller, the projection electrode becomes less robust until only a small amount of connection pressure may cause the projection electrode 52 to be deformed.
Such deformation occurs due to the spherical configuration of the projection electrode 52. The spherical configuration only provides point contact between an end of the projection electrode 52 and the test board 50. Thus, the aforementioned pressure is concentrated on the contact point.
When the projection electrode 52 is deformed, a shorting may occur between the adjacent projection electrodes. A variation in the height of the projection electrodes 52 may also occur, resulting in some of the projection electrodes 52 not being connected to the mounting board when the semiconductor device 51 is mounted on a board.